Decorative windows composed of contoured and textured glass have been made for many generations, reaching a peak in popularity as architectural elements in the last century. Such windows are currently enjoying a revival in popularity, being used particularly as central elements in front doors and as adjacent elements above and beside such doors. Such windows are also being used increasingly in commercial applications for decorative purposes and to form portions of partitions.
Similarly, inserts for mounting at the corners of window of door openings are attaining popularity. Decorative windows and decorative corner inserts are not normally included in the same window opening but their use is a part of the same phenomenon and, indeed the manufacturing techniques also have some similarities.
In the traditional process, such windows and inserts are made from relatively thick plate glass, having various sorts of grooves and other contours ground therein and polished to restore smooth surfaces with desirable optical properties. Certain portions of glass surfaces may be textured using sand blasting, acid etching, or a process called "glue chipping" in which an adhesive applied to a sand blasted surface is stripped to leave a specific pattern. Such windows can also be made as composites of a number of glass panels having deeply beveled edges joined by lead strips contoured for this purpose. Leaded glass windows are quite expensive due to labor costs and breakage during cutting, beveling and assembly.
A number of attempts have been made to simulate traditional decorative windows using various manufacturing processes having lower associated costs. For example, windows with decorative designs and surfaces have been injection molded using clear thermoplastic materials, such as certain types of polycarbonate. However, injection molding has a serious disadvantage in the high cost of the tooling required. The high cost of the dies required in this application is particularly significant, since suppliers of such types of window, corner inserts and associated architectural elements generally need to have an inventory including a large number of window sizes and design patterns. A large number of dies are required and the expense is not practical. Further, injection molded elements have not generally met with commercial success as fine architectural units because they do not look and feel like real glass. Rather, thermoplastic panels are much too flexible compared to glass and transmit and reflect light differently than real glass. In addition, limitations in the ability of the die casting process to produce certain features, such as sharp internal and external edges, detract from the appearance of plastic substitutes for decorative glass panels.
A method for making a solid, continuous plastic part with a textured surface simulating stained glass is described in U.S. Pat. No. 3,848,046. In accordance with this method, a mold is first made by pouring a gel substance into a mold to form a gel layer. Before this layer hardens, an absorbent, such as dry powdered gelatin, is sprinkled on its surface. This powder absorbs moisture, swells, and merges into the gel surface while causing shrinkage of the surface, thereby forming a nodular surface texture. After the gelatin has hardened, a stained glass simulating material, such as polyester resin prepared in a liquid form with a catalyst added, is poured on the textured surface. After the resin hardens, the gelatin mold is dissolved in water and washed off the resin part, which is left as a finished article. In a modification of this process, a hardened plastic framework, including a number of openings, is dropped into the gelatin after the absorbent is added but before the gelatine hardens. Textured resin material is thus allowed to harden in the openings within the framework, simulating a window with multiple panes. While the gelatin mold produced in this process is certainly less expensive than the steel molds required for use in the injection molding process, it is only capable of producing a single finished article. Also, this process produces only a random nodular surface texture; it does not produce pictorial, sculptured designs within the surface of the finished article.
U.S. Pat. No. 3,546,051 describes a method for simulating the overall appearance of a stained glass window by providing a glass pane behind an injection molded plastic framework including a pattern of ribs forming pictorial fields. Various pictorial fields in the pane are colored using stencils. The framework is metallized by the application of metal foil under heat and pressure, by vacuum deposition, or by spraying. While this patent is directed at making a realistic framework, nothing is done about the glass except for coloring.
A method for making simulations of decorative glass panels using thermoplastic films and thin layers of resins adhered to glass panes is described in U.S. Pat. No. 3,713,958. A structure in which a coating of a substantially clear resin, such as an epoxy, vinyl, acrylic, or polyester type, is applied to one side of a glass pane, while light-transmissive glass tint is applied to the opposite side to simulate stained glass. For the resin, a copolymer of N-butyl methacrylate and methyl methacrylate in aromatic solvents was found to be compatible with glass.
U.S. Pat. No. 4,335,170 describes a method of simulating stained and leaded glass panels in which a very thin polyester film is attached to a sheet of glass using an adhesive. Individual film segments are cut to correspond with design segments having different colors. After the adhesive is applied to the film, a soap solution is applied thereon to neutralize the effect of the adhesive during the process of positioning the film on the glass. After the film is positioned on the glass, the soap solution is forced outward by pressure with a squeegee so that adhesion occurs.
U.S. Pat. No. 4,791,010 describes the application of a unique liquid mixture of ink and varnish to a glass pane in order to produce a simulated etched glass appearance. A framework of spacers is then placed atop the glass, adjacent to its edges, surrounding the ink and varnish image, and another glass pane is placed atop the spacers. These items are then formed into a permanent assembly, with the image protected on the inside surface of the first glass pane, as sealing materials are applied around outer surfaces of the spacers.
U.S. Pat. No. 4,154,880 describes a window pane with a decorative molding attached to one surface by an adhesive strip. The molding includes flanges which mechanically lock with the adhesive strip. This patent indicates that areas of the glass adjacent to the molding sections can be of different colors or can have different surface treatments, such as sandblasting.
The methods described in the above paragraphs have the disadvantage of providing only very thin coatings on the glass surfaces. U.S. Pat. No. 3,713,958, discussed above, describes the texturing of the resin with a rod or other tool to provide an irregular or wavy surface but none of the approaches discussed are capable of providing the deeply contoured or sculptured appearance, including recognizable pictorial elements, associated with historically structured decorative windows. Furthermore, none of these techniques can provide the wide variety of surface finishes associated with decorative glass at a reasonable cost.
A method for making a different sort of decorative panel is proposed in U.S. Pat. No. 3,516,893 which provides for printed acetate fabric adhesively attached on one side to a sheet of tempered glass. On the opposite side is a backing sheet, which is preferably methacrylate ester polymer. The adhesive is of a type, such as a mixture of acetone and butyl acetate, which totally or partially dissolves the acetate fibers of the fabric without destroying the color and pattern of the printed design. After the adhesive is cured, the tempered glass is shattered, creating a mosaic effect while retaining its panel form.
A number of patents describe methods for the simulation of multi-pane windows in structures having a continuous pane of glass to which other elements of substantial thickness are attached. For example, U.S. Pat. Nos. 4,495,739 and 4,518,446 describe a decorative window and a method for manufacturing, wherein ornamental lead strips are attached around the edges of one or more glass segments having an edge thickness of about one eighth of an inch, where each glass segment is bonded to an underlying glass pane, and where the strip is held in place by a polysulfide adhesive carried in its channel and mechanically locked by inwardly directed flanges at its edges. U.S. Pat. No. 4,904,513 describes a plurality of plates with beveled edges being adhesively attached to a single backing pane of glass, preferably through the use of a layer of polyvinyl butyrate under conditions of heat and pressure. In one variation, decorative strips are also glued in place between the beveled plates.
Some prior art patents describe either modifying a single glass pane to look like a multi-pane window, or alternately and additionally, attaching one or more additional pieces of glass to a backing pane. For example, U.S. Pat. No. 4,488,919 describes methods for making a simulated multi-pane beveled and leaded glass window by forming beveled groves to subdivide a glass or plastic plate, with smooth surfaces on both sides, into design segments of unrelieved panels. Lead strips are subsequently attached to the flat bottom walls of these grooves, which are preferably formed by machining. In an alternate method, the panel can be formed by injection molding. In another alternative construction, segments having a substantial thickness, such as sheets of glass, polycarbonate, or poly(methylacrylate) up to about one quarter inch in thickness, may be laminated to a base pane.
Certain design segments can be provided with a jeweled glass appearance by securing transparent shapes, having flat inner surface and faceted or smoothly curved outer surfaces, in place using a pressure-sensitive adhesive. U.S. Pat. No. 4,619,850 describes the attachment of a die cast lead component to each side of a sheet of glass, thereby simulating lead strips holding individual pieces of glass. Surface treatments, such as coloring, sand blasting, or "glue chipping" conventionally applied to decorative glass windows may be applied if desired to various zones of the glass. In a modified version, a bevelled glass layer is adhesively bonded to a zone within the lead components.
U.S. Pat. Nos. 1,709,267; 3,580,192; and 4,283,894 illustrate decorative corner structure to be mounted in a window frame, door frame or simply at the intersection of two wall structures. Mounting techniques used in these three patents are diverse and indeed they are quite different from the mounting structures of the panels described above because they are concerned with generally triangular shaped elements not extending completely across the opening within a framework. Uniformly the mounting techniques are difficult to the extent that they often become problems to provide stability to the corner insert.
One method of replicating an article such as a surface configuration is to form a mold over the surface of the original article using liquid silicone. The formed mold may thereafter be filled with a resin, which is allowed to cure within the mold before it is removed as a replica. Traditional mold release agents, such as Teflon or silicone sprays have been used to prevent adhesion between the mold material and the cured resin replica articles. Such agents have also been used to facilitate the removal of molds poured around original objects. Such mild release agents are applied to the surface of the original object before the mold is made, and/or to the mold itself before the addition of material to be molded into a replica.
The removal of a silicone mold from a glass master such as used in this invention poses particular problems. The adhesive forces between the silicone and the glass are so great that as few as one in twenty molds is successfully removed from the master without serious damage using conventional prior art mold release agents. Furthermore, the use of traditional mold release agents, applied to the master before pouring the mold, renders the mold unacceptable for producing replicas of adequate quality since the release agents leave impressions in the mold which are subsequently transferred to the replicas as roughened surfaces. Due to the intended use of replicas to transmit light and to produce aesthetic effects similar to those produced by cut and polished glass surfaces, the production of plastic decorative glass replicas is much more sensitive to blemishes than is the production of virtually all other plastic parts by molding processes.
One potential solution to the prior art problems of using the decorative glass replica in architectural applications is to form the plastic decorative layer on a conventional glass pane, which then acts as a backing for the decorative plastic layer. A technical problem still requiring resolution is the adhesion between a cured resin plastic layer and the glass pane used as the backing plate. Excellent adhesion is required, so that the resulting decorative windows can be used in exterior architectural applications without delamination occurring due to large amount of thermal expansion which occurs between hot summer days and cold winter nights. A solution to this problem is disclosed in pending application Ser. No. 807,236 and to the extent necessary for a full understanding of this invention it is incorporated herein by reference.